Combustion of Oil From a Marine Oil Spill

ABSTRACT

Method and apparatus for burning oil from an oil release in a body of water. A mixture of oil and water is collected from the surface of the body of water and separated into an oil-enriched portion and a water-enriched portion. The oil-enriched portion is passed to a burner where the oil-enriched portion is combusted with an oxygen-containing gas having an oxygen concentration of at least 25 volume % oxygen.

BACKGROUND

The BP oil spill in the Gulf of Mexico resulted in large areas of crude oil floating on the ocean surface. Some of these areas are close to beaches or natural habitats of animals. Mechanical recovery, chemical treatment, bioremediation, and in-situ burning are amongst the most widely practiced marine oil spill response technologies.

While large scale skimming is one method to control oil pollution, the U.S. Coast Guard has been conducting in-situ burns of the surface oil, primarily due to the advantages associated with this technology such as high oil removal rates, relatively low cost, and simple logistics.

The U.S. Coast Guard issued an operations manual for in-situ burning of oil from oil spills as U.S. Coast Guard Research and Development Center Report No. CG-D-06-03, Oil Spill Response Offshore, In-Situ Burn Operations Manual, Final Report, March 2003 (hereinafter, Coast Guard Manual). The Coast Guard Manual may be referred to for conventional in-situ burning of oil pools floating on water.

The problem of burning oil in the ocean surface is that favorable combustion conditions are rarely achievable, particularly towards the center of the fire where oxygen availability is limited due to lack of air entrainment. As a result, a black smoke plume from the in-situ burn can rise hundreds or even thousands of meters. The Coast Guard Manual described adding chemical smoke inhibitors such as ferrocene. But its use is not approved due to high cost, difficulty of applying, and potential toxicity. While the black smoke may have less environmental impact than the oil slick, the public generally finds the black smoke plume objectionable.

A further problem of the in-situ burn is that a substantial amount of oil is still left unburned after the fire self-extinguishes, that is, after a minimum flame-sustainable oil layer thickness is reached as reported in the Coast Guard Manual.

A method to burn the oil cleanly with substantially less smoke and/or to reduce the residual oil after fire extinction is desired.

Another problem with oil floating on water is the formation of a stable water-in-oil emulsion which will reduce the window of opportunity for in-situ burning. The presence of a critical amount of water in the oil prevents the slick in contact with the ignition source from catching fire as reported in the Coast Guard Manual.

A method to burn stable water-in-oil emulsions is desired.

Another problem with in-situ burn is that it is inherently ‘not controlled’, i.e., once the oil slick is ignited and unless the fire is intentionally extinguished, the combustion continues until the fire self-extinguishes naturally when the slick burns down to a thickness that allows enough heat to pass through the slick to the water to cool the surface of the oil below its flash point. Furthermore, the firing rate during an in-situ burn cannot be controlled because it depends on a wide variety of external factors which operators have no control over, such as wind speed and wind direction, wave frequency and wave amplitude, composition of slick, stability of water-oil emulsions, and non-uniform slick thickness over the area of oil pool enclosed by booms.

A method for controlled burning of oil and water-in-oil emulsions is desired.

BRIEF SUMMARY

The present invention relates to a method and apparatus for burning oil from an oil release in a body of water.

There are several aspects of the process as outlined below.

Aspect 1. A method comprising:

-   -   collecting a mixture of oil and water from the surface of the         body of water;     -   separating the collected mixture into an oil-enriched portion         and a water-enriched portion;     -   returning the water-enriched portion to the body of water; and     -   passing an oxygen-containing gas and the oil-enriched portion to         a burner on board a marine vessel and combusting the         oil-enriched portion with the oxygen-containing gas thereby         generating a flame;     -   wherein the oxygen-containing gas comprises at least 25 volume %         oxygen.

Aspect 2. The method of aspect 1 further comprising:

-   -   measuring a temperature responsive to a temperature of the         flame;     -   adjusting at least one of (i) the oxygen concentration in the         oxygen-containing gas, and (ii) the flow rate of the         oil-enriched portion, responsive to the measured temperature.

Aspect 3. The method of aspect 1 or aspect 2 further comprising:

-   -   passing an air feed stream to an adsorption system on board the         marine vessel;     -   separating the air feed stream into an oxygen product stream and         waste gas stream in the adsorption system; and     -   withdrawing the oxygen product stream and the waste gas stream         from the adsorption system;     -   wherein the oxygen-containing gas comprises the oxygen product         stream.

Aspect 4. The method of aspect 3 further comprising:

-   -   generating electrical power by combusting a fuel in a turbine         that drives an electric generator wherein the turbine and the         electric generator are on board the marine vessel;     -   wherein the electrical power generated by combusting the fuel is         used in the step of separating the air feed stream.

Aspect 5. The method of aspect 3 wherein the oil-enriched portion is combusted with the oxygen-containing gas in a boiler thereby generating steam wherein the boiler is on board the marine vessel, the method further comprising:

-   -   passing the steam to a steam turbine to generate electrical         power wherein the steam turbine is on board the marine vessel;     -   wherein the electrical power generated by the steam turbine is         used in the step of separating the air feed stream.

Aspect 6. The method of any one of aspects 1 to 4 wherein the oil-enriched portion is combusted in a furnace thereby forming combustion product gases wherein the furnace is on board the marine vessel, the method further comprising:

-   -   heating the oxygen-containing gas by indirect heat transfer with         the combustion product gases.

Aspect 7. The method of any one of aspects 1 to 4 wherein the oil-enriched portion is combusted in a furnace thereby forming combustion product gases wherein the furnace is on board the marine vessel, the method further comprising:

-   -   heating the oil-enriched portion by indirect heat transfer with         the combustion product gases prior to combusting the         oil-enriched portion.

Aspect 8. The method of any one of aspects 1 to 7 wherein the oil in the mixture of oil and water comprises residual oil from in-situ burning of an oil pool floating on the body of water.

Aspect 9. An apparatus comprising:

-   -   a skimmer for collecting a mixture of oil and water from the         surface of the body of water;     -   a separator for separating the collected mixture into an         oil-enriched portion and a water-enriched portion;     -   at least one of an oxygen generator and an oxygen storage tank         on board a marine vessel; and     -   a burner on board the marine vessel configured to receive the         oil-enriched portion and oxygen from the at least one of the         oxygen generator and the oxygen storage tank.

Aspect 10. The apparatus of aspect 9 further comprising:

-   -   a temperature sensor for sensing a temperature responsive to a         temperature of a flame emanating from the burner;     -   a controller in signal communication with the temperature         sensor;     -   a valve in signal communication with the controller for         regulating the flow of oxygen from the at least one of the         oxygen generator and the oxygen storage tank.

Aspect 11. The apparatus of aspect 9 or aspect 10 further comprising:

-   -   a temperature sensor for sensing a temperature responsive to a         temperature of a flame emanating from the burner;     -   a controller in signal communication with the temperature         sensor;     -   a second valve in signal communication with the controller for         regulating the flow of oil-enriched portion from the separator.

Aspect 12. The apparatus of any one of aspects 9 to 11 wherein the apparatus comprises the oxygen generator and wherein the oxygen generator is an adsorption system.

Aspect 13. The apparatus of aspect 12 further comprising:

-   -   a turbine on board the marine vessel;     -   an electric generator on board the marine vessel, the electric         generator driven by the turbine; and     -   a fuel storage tank on board the marine vessel, the fuel storage         tank configured to deliver fuel to the turbine;     -   wherein the electric generator is configured to provide         electrical power to the adsorption system.

Aspect 14. The apparatus of aspect 12 further comprising:

-   -   a boiler on board the marine vessel for receiving a flame from         the burner and generating steam from the combustion of the         oil-enriched portion; and     -   a steam turbine on board the marine vessel for receiving steam         from the boiler and generating electrical power;     -   wherein the steam turbine is configured to provide electrical         power to the adsorption system.

Aspect 15. The apparatus of any one of aspects 9 to 14 further comprising:

-   -   a furnace on board the marine vessel configured to receive a         flame from the burner, the furnace having an exhaust for         expelling combustion product gases;     -   a heat exchanger on board the marine vessel configured to         receive the combustion product gases from the furnace to         transfer heat from the combustion product gases to the oxygen by         indirect heat transfer.

Aspect 16. The apparatus of any one of aspects 9 to 14 further comprising:

-   -   a furnace on board the marine vessel configured to receive a         flame from the burner, the furnace having an exhaust for         expelling combustion product gases;     -   a heat exchanger on board the marine vessel configured to         receive the combustion product gases from the furnace to         transfer heat from the combustion product gases to the         oil-enriched portion by indirect heat transfer.

Aspect 17. The method of any one of aspects 1 to 8 further comprising providing any one of the apparatuses of aspects 9 to 16.

BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS

The FIGURE is a schematic of an apparatus for collecting and burning oil from an oil release in a body of water.

DETAILED DESCRIPTION

The articles “a” and “an” as used herein mean one or more when applied to any feature in embodiments of the present invention described in the specification and claims. The use of “a” and “an” does not limit the meaning to a single feature unless such a limit is specifically stated. The article “the” preceding singular or plural nouns or noun phrases denotes a particular specified feature or particular specified features and may have a singular or plural connotation depending upon the context in which it is used. The adjective “any” means one, some, or all indiscriminately of whatever quantity. The term “and/or” placed between a first entity and a second entity means one of (1) the first entity, (2) the second entity, and (3) the first entity and the second entity. The term “and/or” placed between the last two entities of a list of 3 or more entities means at least one of the entities in the list.

The present invention relates to a method and apparatus for burning oil from an oil release in a body of water.

The apparatus and method are described with reference to the FIGURE, which illustrates an exemplary apparatus of the invention. While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and are herein described in detail. It should be understood, however that the description herein of specific embodiments is not intended to limit the invention to the particular forms disclosed, but on the contrary, the invention is to cover all modifications, equivalents, and alternatives falling within the scope of the invention as defined by the appended claims.

The method comprises collecting a mixture of oil and water 115 from the surface of a body of water. The oil may be refined oil, unrefined crude oil, or any hydrocarbon-based flammable or combustible mixture in substantially liquid phase. The oil may be oil that has leaked from a vessel or pipeline. The oil may be oil that has leaked from a well. The mixture may be an emulsion containing oil and water.

The body of water may be an ocean, sea, lake, river, and the like.

While the various components are shown on board a single marine vessel 100, the components may be distributed among one or more marine vessels, consistent with the meaning of the articles “a” and “an” being used to mean one or more when applied to any feature.

Marine vessel 100 may be any marine vessel, for example a barge, boat, ship, and the like.

Boom 110 may be attached to marine vessel 100 for gathering floating oil. The mixture of oil and water is collected through skimmer 120. The skimmer may be any commercially available skimmer, for example, a Magnum series skimmer by Elastec American Marine.

The mixture is pumped via pump 10 to separator 20. Separator 20 separates the collected mixture of oil and water into an oil-enriched portion 22 and a water-enriched portion 24. The oil-enriched portion has a higher concentration of oil than the water-enriched portion. The water-enriched portion has a higher concentration of water than the oil-enriched portion. The separator may be any known separator for separating an oil-enriched portion from a water-enriched portion, for example, a settling tank or a centrifuge. The water-enriched portion 24 is returned to the body of water.

The oil-enriched portion 22 is passed from the separator 20 via pump 25 to burner 170 on board the marine vessel for combustion of the oil-enriched portion. The flow rate of the oil-enriched portion is regulated by valve 160. The oil-enriched portion may be temporarily stored in a storage tank (not shown).

Burner 170 may be of any suitable type capable of using liquid fuel and of sufficient capacity. The burner is configured to receive the oil-enriched portion and oxygen from the at least one of the oxygen generator and the oxygen storage tank.

An oxygen-containing gas 65 is passed to burner 170 for combusting the oil-enriched portion 22 thereby generating a flame. Some of the oil-enriched portion may be burned using compressed air passed to the burner. According to the method disclosed herein, however, the oxygen-containing gas comprises at least 25 volume % oxygen for at least a portion of the combustion process.

The oxygen-containing gas comprising at least 25 volume % oxygen may be formed from mixing air with industrial grade oxygen. The industrial grade oxygen is supplied by at least one of an oxygen generator and an oxygen storage tank on board the marine vessel. The industrial grade oxygen may be from any known source, for example, a vacuum swing adsorber (VSA), a cryogenic oxygen generator, liquid oxygen stored in a cryogenic vessel, or oxygen stored as a compressed gas.

A temperature sensor 180 senses a temperature responsive to a temperature of a flame emanating from the burner 170. The temperature sensor 180 is in signal communication with controller 210. The communication may be hardwired and/or wireless. Controller 210 controls the oxygen concentration in the oxygen-containing gas responsive to the measured temperature by adjusting various valves, pumps, etc. The various valves, pumps, blowers may also be in signal communication with controller 210. This aspect is particularly useful when the water content in the oil-enriched portion increases. As the temperature measured by the sensor drops, the oxygen concentration in the oxygen-containing gas is increased to enhance the combustion of the oil-enriched portion as the water content increases.

The FIGURE shows industrial grade oxygen made by adsorption system 200, a VSA on board the marine vessel 100. The adsorption system comprises two or more adsorption beds containing adsorbent selective for nitrogen. Air 15 is filtered in filter 70, compressed in blower 40, and passed to the inlet of the adsorption system 200 as air feed stream 35. The air feed stream is separated into an oxygen product stream 205 and a waste gas stream 135 in the adsorption system. The oxygen product stream 205 is withdrawn from adsorption system 200 via valve 50. The oxygen product stream 205 is blended with air to form the oxygen-containing gas, compressed in compressor 80, and passed to burner 170. The flow rate of the oxygen-containing gas is regulated via valve 60. Waste gas 135 depleted in oxygen is withdrawn from the adsorption system via blower 130. The adsorption system may be a PRISM® VSA Oxygen Generation system available from Air Products and Chemicals, Inc.

As shown in the FIGURE, electrical power for the various pumps, blowers, compressors, controllers, air separation system, etc. is provided by turbine 30. Turbine 30 drives electric generator 150. Turbine 30 and electric generator 150 are shown on board marine vessel 100. Turbine 30 may be a diesel powered gas turbine available from General Electric Co. Fuel tank 140 provides fuel for turbine 30. Air, filtered in filter 70, is provided to the turbine 30.

The oil-enriched portion may be combusted with the oxygen-containing gas in a boiler (not shown) there by generating steam. The steam may be passed to a steam turbine to generate electrical power for the various electricity consumption needs on board the vessel.

The oil-enriched portion may be combusted in a furnace (not shown) thereby forming combustion products gases. The combustion product gases may be used to heat the oxygen-containing gas by indirect heat transfer. Preheating the oxygen-containing gas improves the ability to combust the oil-enriched portion.

The oil-enriched portion may be combusted in a furnace (not shown) thereby forming combustion product gases. The combustion product gases may be used to heat the oil-enriched portion by indirect heat transfer. Preheating the oil-enriched portion improves the ability to combust the oil-enriched portion.

The present method may be used in conjunction with any known in-situ burning of oil pools floating on water. An in-situ burn of the floating oil may be performed initially and the residual oil from the in-situ burn collected for burning with an oxygen-containing gas comprising at least 25 volume % oxygen using the burner. The oil in the mixture of oil and water may comprise residual oil from in-situ burning of an oil pool floating on the body of water.

Example

The stoichiometric oxygen requirement for combusting 200 BPH (barrels per hour) oil flow rate is calculated to be about 60,000 Nm³/hr. If the stoichiometric amount of oxygen is supplied by injecting compressed air, the compressed air flow rate is about 285,000 Nm³/hr.

If the stoichiometric amount of oxygen is supplied by injecting an oxygen-containing gas wherein the oxygen-containing gas has 50 volume % oxygen, the total flow rate of the oxygen-containing gas is about 204,000 Nm³/hr. The flow rate of substantially pure industrial oxygen (90-93 vol. % O₂, typical VSA quality) is about 24,000 Nm³/hr and the balance compressed air.

If half of the stoichiometric amount oxygen is supplied by injecting an oxygen-containing gas wherein the oxygen-containing gas has 50 volume % oxygen, the total flow rate of the oxygen-containing gas is about 102,000 Nm³/hr. The flow rate of substantially pure industrial oxygen (90-93% VSA spec) is about 12,000 Nm₃/hr and the balance compressed air. The other half of the stoichiometric amount of oxygen is supplied by ambient air surrounding the flame. 

We claim:
 1. A method for burning oil from an oil release in a body of water, the method comprising: collecting a mixture of oil and water from the surface of the body of water; separating the collected mixture into an oil-enriched portion and a water-enriched portion; returning the water-enriched portion to the body of water; passing an oxygen-containing gas and the oil-enriched portion to a burner on board a marine vessel and combusting the oil-enriched portion with the oxygen-containing gas thereby generating a flame; measuring a temperature responsive to a temperature of the flame; and adjusting the oxygen concentration in the oxygen-containing gas responsive to the measured temperature; wherein the oxygen-containing gas is at least 25 volume % oxygen.
 2. (canceled)
 3. The method of claim 1 further comprising: passing an air feed stream to an adsorption system on board the marine vessel; separating the air feed stream into an oxygen product stream and waste gas stream in the adsorption system; and withdrawing the oxygen product stream and the waste gas stream from the adsorption system; wherein the oxygen-containing gas comprises the oxygen product stream.
 4. The method of claim 3 further comprising: generating electrical power by combusting a fuel in a turbine that drives an electric generator wherein the turbine and the electric generator are on board the marine vessel; wherein the electrical power generated by combusting the fuel is used in the step of separating the air feed stream. 5-7. (canceled)
 8. The method of claim 1 wherein the oil in the mixture of oil and water comprises residual oil from in-situ burning of an oil pool floating on the body of water.
 9. An apparatus for burning oil from an oil release in a body of water, the apparatus comprising: a skimmer for collecting a mixture of oil and water from the surface of the body of water; a separator for separating the collected mixture into an oil-enriched portion and a water-enriched portion; at least one of an oxygen generator and an oxygen storage tank on board a marine vessel; a burner on board the marine vessel configured to receive the oil-enriched portion and oxygen from the at least one of the oxygen generator and the oxygen storage tank; a temperature sensor for sensing a temperature responsive to a temperature of a flame emanating from the burner; a controller in signal communication with the temperature sensor; and a valve in signal communication with the controller for regulating the flow of oxygen from the at least one of the oxygen generator and the oxygen storage tank to form an oxygen-containing gas formed from mixing air with the oxygen from the at least one of the oxygen generator and the oxygen storage tank; wherein the controller controls the oxygen concentration in the oxygen-containing gas responsive to the temperature sensed by the temperature sensor by adjusting the valve.
 10. (canceled)
 11. The apparatus of claim 9 further comprising: a temperature sensor for sensing a temperature responsive to a temperature of a flame emanating from the burner; a controller in signal communication with the temperature sensor; and a second valve in signal communication with the controller for regulating the flow of oil-enriched portion from the separator.
 12. The apparatus of claim 9 wherein the apparatus comprises the oxygen generator and wherein the oxygen generator is an adsorption system.
 13. The apparatus of claim 12 further comprising: a turbine on board the marine vessel; an electric generator on board the marine vessel, the electric generator driven by the turbine; and a fuel storage tank on board the marine vessel, the fuel storage tank configure to deliver fuel to the turbine; wherein the electric generator is configured to provide electrical power to the adsorption system. 14-16. (canceled) 